It was at least 5 years since I struggled with this. The map should show a gradient with values like 0, 1-19, 20-39 and so on. A lot of classes, and I found out that records with a column with null value were returned as value 0 and therefore ended up in class expression ( x = [0]) together with real values = 0. That is why I created two layers with the same name as I described in my first mail. However, if you have no need to differ between 0 and null I think you can either have a class with expression ( x=[0]), or perhaps as Richard G suggested no expression at all, which would be simplest.
Björn D ________________________________ Från: MapServer-users <mapserver-users-boun...@lists.osgeo.org> för Richard Greenwood via MapServer-users <mapserver-users@lists.osgeo.org> Skickat: den 28 mars 2025 16:19 Kopia: angelique.kro...@stadt-koeln.de <angelique.kro...@stadt-koeln.de>; MapServer Users <mapserver-users@lists.osgeo.org> Ämne: Re: [MapServer-users] NULL-EXPRESSION Have you tried making your CLASS for NULLs the last of the three classes and with no EXPRESSION? The first two classes would pick up 2000 and 2100 and then anything not matching would be in the third class. This works in most cases but I haven't tried it with NULLs. Rich On Fri, Mar 28, 2025 at 4:36 AM Björn Danielsson via MapServer-users <mapserver-users@lists.osgeo.org<mailto:mapserver-users@lists.osgeo.org>> wrote: This works for me. Try this: Create two layers with the same name and group. Layer 1 ( takes care of values 2000 and 2100) : LAYER NAME "A" GROUP "A" ..... PROCESSING 'NATIVE_FILTER=gst IS NOT NULL' CLASS for 2000 .... CLASS for 2100 .... END Layer 2 ( value = NULL ) ❤️ LAYER NAME "A" GROUP "A" .... PROCESSING 'NATIVE_FILTER=gst IS NULL' CLASS for NULL .... END ________________________________ Från: MapServer-users <mapserver-users-boun...@lists.osgeo.org<mailto:mapserver-users-boun...@lists.osgeo.org>> för Seth G via MapServer-users <mapserver-users@lists.osgeo.org<mailto:mapserver-users@lists.osgeo.org>> Skickat: den 28 mars 2025 10:43 Till: angelique.kro...@stadt-koeln.de<mailto:angelique.kro...@stadt-koeln.de> <angelique.kro...@stadt-koeln.de<mailto:angelique.kro...@stadt-koeln.de>>; MapServer Users <mapserver-users@lists.osgeo.org<mailto:mapserver-users@lists.osgeo.org>> Ämne: Re: [MapServer-users] NULL-EXPRESSION Hi, Unfortunately, MapServer doesn't have a NULL type. The workaround is to create a database view or query that will set the NULL to a numeric value of your choosing, e.g. -1 and then use that value in the CLASS expressions. Seth -- web:https://geographika.net & https://mapserverstudio.net mastodon: @geographika@mastodon.social<mailto:geographika@mastodon.social> On Fri, Mar 28, 2025, at 8:55 AM, Angelique Kroisl via MapServer-users wrote: Hello, I'm trying to create a class using the class item "gst." The attribute in the database can only have three values (2000, 2100, and <NULL>). Unfortunately, I can't create the NULL EXPRESSION. I've already tried the following: EXPRESSION IS NULL EXPRESSION "<NULL>" EXPRESSION <NULL> EXPRESSION EMPTY What is the correct syntax for this? ________________________________ Monatlich aktuelle Informationen Ihrer Stadtverwaltung in unserem Newsletter! Newsletter Anmeldung<https://www.stadt-koeln.de/service/onlinedienste/newsletter-anmeldung?para=allgemein> ________________________________ [X]<https://www.stadt-koeln.de/leben-in-koeln/freizeit-natur-sport/veranstaltungskalender/lidl-final4-dhb-pokal> _______________________________________________ MapServer-users mailing list MapServer-users@lists.osgeo.org<mailto:MapServer-users@lists.osgeo.org> https://lists.osgeo.org/mailman/listinfo/mapserver-users _______________________________________________ MapServer-users mailing list MapServer-users@lists.osgeo.org<mailto:MapServer-users@lists.osgeo.org> https://lists.osgeo.org/mailman/listinfo/mapserver-users -- Richard W. Greenwood www.greenwoodmap.com<http://www.greenwoodmap.com>
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